CI: don't fetch the whole git history if it's not required (#9021)

## Problem
We do use `actions/checkout` with `fetch-depth: 0` when it's not
required

## Summary of changes
- Remove unneeded `fetch-depth: 0`
- Add a comment if `fetch-depth: 0` is required

.github/workflows/build_and_test.yml

@@ -54,8 +54,8 @@ jobs:
       build-tag: ${{steps.build-tag.outputs.tag}}
 
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      # Need `fetch-depth: 0` to count the number of commits in the branch
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
@@ -374,8 +374,8 @@ jobs:
         coverage-html: ${{ steps.upload-coverage-report-new.outputs.report-url }}
         coverage-json: ${{ steps.upload-coverage-report-new.outputs.summary-json }}
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      # Need `fetch-depth: 0` for differential coverage (to get diff between two commits)
+      - uses: actions/checkout@v4
         with:
           submodules: true
           fetch-depth: 0
@@ -476,11 +476,9 @@ jobs:
     runs-on: ${{ fromJson(format('["self-hosted", "{0}"]', matrix.arch == 'arm64' && 'large-arm64' || 'large')) }}
 
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      - uses: actions/checkout@v4
         with:
           submodules: true
-          fetch-depth: 0
 
       - uses: ./.github/actions/set-docker-config-dir
       - uses: docker/setup-buildx-action@v3
@@ -555,11 +553,9 @@ jobs:
     runs-on: ${{ fromJson(format('["self-hosted", "{0}"]', matrix.arch == 'arm64' && 'large-arm64' || 'large')) }}
 
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      - uses: actions/checkout@v4
         with:
           submodules: true
-          fetch-depth: 0
 
       - uses: ./.github/actions/set-docker-config-dir
       - uses: docker/setup-buildx-action@v3
@@ -706,10 +702,7 @@ jobs:
       VM_BUILDER_VERSION: v0.29.3
 
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
+      - uses: actions/checkout@v4
 
       - name: Downloading vm-builder
         run: |
@@ -749,10 +742,7 @@ jobs:
     runs-on: ${{ fromJson(format('["self-hosted", "{0}"]', matrix.arch == 'arm64' && 'small-arm64' || 'small')) }}
 
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
+      - uses: actions/checkout@v4
 
       - uses: ./.github/actions/set-docker-config-dir
       - uses: docker/login-action@v3
@@ -977,10 +967,7 @@ jobs:
             git config --global --add safe.directory "${GITHUB_WORKSPACE}/vendor/postgres-v$r"
           done
 
-      - name: Checkout
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
+      - uses: actions/checkout@v4
 
       - name: Trigger deploy workflow
         env:

.github/workflows/trigger-e2e-tests.yml

@@ -34,8 +34,8 @@ jobs:
       build-tag: ${{ steps.build-tag.outputs.tag }}
 
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      # Need `fetch-depth: 0` to count the number of commits in the branch
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0